Add developer test writing guide for Patrole tests
This patch set doesn't really add new documentation but instead
moves documentation regarding RBAC testing guidelines and
examples out of framework/rbac_utils.rst and moves it into a
separate test_writing_guide.rst file located in the
"Developers' Guide" section.
This is because this information is directly relevant to developers
and should be included somewhere obvious where they can find it.
Including important testing examples and guidelines in the framework
documentation isn't too helpful.
Change-Id: I6e975cbf1b86d356e9f5d623f81fbf293efcc42c
diff --git a/doc/source/test_writing_guide.rst b/doc/source/test_writing_guide.rst
new file mode 100644
index 0000000..d25f60a
--- /dev/null
+++ b/doc/source/test_writing_guide.rst
@@ -0,0 +1,166 @@
+Patrole Test Writing Overview
+=============================
+
+Introduction
+------------
+
+Patrole tests are broken up into 3 stages:
+
+#. :ref:`rbac-test-setup`
+#. :ref:`rbac-test-execution`
+#. :ref:`rbac-test-cleanup`
+
+See the :ref:`framework overview documentation <framework-overview>` for a
+high-level explanation of the entire testing work flow and framework
+implementation. The guide that follows is concerned with helping developers
+know how to write Patrole tests.
+
+.. _role-overriding:
+
+Role Overriding
+---------------
+
+Role overriding is the way Patrole is able to create resources and delete
+resources -- including those that require admin credentials -- while still
+being able to exercise the same set of Tempest credentials to perform the API
+action that authorizes the policy under test, by manipulating the role of
+the Tempest credentials.
+
+Patrole implicitly splits up each test into 3 stages: set up, test execution,
+and teardown.
+
+The role workflow is as follows:
+
+#. Setup: Admin role is used automatically. The primary credentials are
+ overridden with the admin role.
+#. Test execution: ``[patrole] rbac_test_role`` is used manually via the
+ call to ``with rbac_utils.override_role(self)``. Everything that
+ is executed within this contextmanager uses the primary
+ credentials overridden with the ``[patrole] rbac_test_role``.
+#. Teardown: Admin role is used automatically. The primary credentials have
+ been overridden with the admin role.
+
+.. _rbac-test-setup:
+
+Test Setup
+----------
+
+Automatic role override in background.
+
+Resources can be set up inside the ``resource_setup`` class method that Tempest
+provides. These resources are typically reserved for "expensive" resources
+in terms of memory or storage requirements, like volumes and VMs. These
+resources are **always** created via the admin role; Patrole automatically
+handles this.
+
+Like Tempest, however, Patrole must also create resources inside tests
+themselves. At the beginning of each test, the primary credentials have already
+been overridden with the admin role. One can create whatever test-level
+resources one needs, without having to worry about permissions.
+
+.. _rbac-test-execution:
+
+Test Execution
+--------------
+
+Manual role override required.
+
+"Test execution" here means calling the API endpoint that enforces the policy
+action expected by the ``rbac_rule_validation`` decorator. Test execution
+should be performed *only after* calling
+``with rbac_utils.override_role(self)``.
+
+Immediately after that call, the API endpoint that enforces the policy should
+be called.
+
+Examples
+^^^^^^^^
+
+Always use the contextmanager before calling the API that enforces the
+expected policy action.
+
+Example::
+
+ @rbac_rule_validation.action(
+ service="nova",
+ rule="os_compute_api:os-aggregates:show")
+ def test_show_aggregate_rbac(self):
+ # Do test setup before the ``override_role`` call.
+ aggregate_id = self._create_aggregate()
+ # Call the ``override_role`` method so that the primary credentials
+ # have the test role needed for test execution.
+ with self.rbac_utils.override_role(self):
+ self.aggregates_client.show_aggregate(aggregate_id)
+
+When using a waiter, do the wait outside the contextmanager. "Waiting" always
+entails executing a ``GET`` request to the server, until the state of the
+returned resource matches a desired state. These ``GET`` requests enforce
+a different policy than the one expected. This is undesirable because
+Patrole should only test policies in isolation from one another.
+
+Otherwise, the test result will be tainted, because instead of only the
+expected policy getting enforced with the ``os_primary`` role, at least
+two policies get enforced.
+
+Example using waiter::
+
+ @rbac_rule_validation.action(
+ service="nova",
+ rule="os_compute_api:os-admin-password")
+ def test_change_server_password(self):
+ original_password = self.servers_client.show_password(
+ self.server['id'])
+ self.addCleanup(self.servers_client.change_password, self.server['id'],
+ adminPass=original_password)
+
+ with self.rbac_utils.override_role(self):
+ self.servers_client.change_password(
+ self.server['id'], adminPass=data_utils.rand_password())
+ # Call the waiter outside the ``override_role`` contextmanager, so that
+ # it is executed with admin role.
+ waiters.wait_for_server_status(
+ self.servers_client, self.server['id'], 'ACTIVE')
+
+Below is an example of a method that enforces multiple policies getting
+called inside the contextmanager. The ``_complex_setup_method`` below
+performs the correct API that enforces the expected policy -- in this
+case ``self.resources_client.create_resource`` -- but then proceeds to
+use a waiter.
+
+Incorrect::
+
+ def _complex_setup_method(self):
+ resource = self.resources_client.create_resource(
+ **kwargs)['resource']
+ self.addCleanup(test_utils.call_and_ignore_notfound_exc,
+ self._delete_resource, resource)
+ waiters.wait_for_resource_status(
+ self.resources_client, resource['id'], 'available')
+ return resource
+
+ @rbac_rule_validation.action(
+ service="example-service",
+ rule="example-rule")
+ def test_change_server_password(self):
+ # Never call a helper function inside the contextmanager that calls a
+ # bunch of APIs. Only call the API that enforces the policy action
+ # contained in the decorator above.
+ with self.rbac_utils.override_role(self):
+ self._complex_setup_method()
+
+To fix this test, see the "Example using waiter" section above. It is
+recommended to re-implement the logic in a helper method inside a test such
+that only the relevant API is called inside the contextmanager, with
+everything extraneous outside.
+
+.. _rbac-test-cleanup:
+
+Test Cleanup
+------------
+
+Automatic role override in background.
+
+After the test -- no matter whether it ended successfully or in failure --
+the credentials are overridden with the admin role by the Patrole framework,
+*before* ``tearDown`` or ``tearDownClass`` are called. This means that
+resources are always cleaned up using the admin role.